ABSTRACT 9724006 RABINOW Dr. Rabinow's laboratory is characterizing a Drosophila gene known as Doa, which encodes a member of the LAMMER kinases, a recently discovered eukaryotic family of protein kinases. Protein kinases transfer phosphate groups to other proteins as a means of regulating their activity, and regulate many essential cellular processes. Homologues to Doa throughout the animal kingdom have very similar amino-acid sequences in the part of the protein that has enzymatic activity, suggesting that they have equally similar function in cellular processes. Recessive Doa mutations in flies are almost lethal; however, rare adults do survive, but show defects in eye development. Other defects in Doa mutants include failure of a normal embryonic central nervous system (CNS) to develop and segmentation defects. The DOA kinase is widely expressed and is found at particularly high levels in the embryonic CNS, where rapid cell division and differentiation occurs. The DOA kinase comes in two major forms that differ in size. The larger of these (105 kD) is found only in the cell cytoplasm, whereas the smaller version (55 kD) is also found in the cell nucleus. The structure of the 105 kD cytoplasmic form is completely unknown. In the current research project, Dr. Rabinow's laboratory will carry out further structural and functional characterization of DOA kinase to define the role of this kinase family in the initiation and maintenance of cellular differentiation. The first task will be to determine the structure of the 105 kD protein. In addition, antibodies against the two protein isoforms will be generated to examine their expression. Drosophila expressing specifically altered forms of the kinase will be constructed to determine whether the two protein isoforms perform different functions, as well as to provide more complete genetic characterization of Doa mutant defects. These data will be used to identify one or more of the cellular processes that are altered in mutants. R esults from this project will substantially advance the long-term goal of elucidating the specific cellular functions of the LAMMER protein kinase family and the developmental signaling pathway(s) in which they function.
